by Richard J. Petschauer
A skeptic that believes in global warming? How can that be? We have been told that climate skeptics, sometime incorrectly called “deniers”, still believe the earth is flat and disagree with 97% of scientists. Well, first of all, most of us have seen a globe and know what it represents. Second, do you know on what these scientists agree? If not, don’t feel bad. Those making these claims, mostly politicians, probably don’t know either. Actually, a rather poor survey was done looking at a summary of many technical papers. If any one of many climate related points were made, they were put in the 97% camp. This article would probably have qualified too.
But the real question, not covered in the survey: How fast will the earth warm if we do nothing to curtail the growth of man made carbon dioxide emissions? And how much can we reduce the warming if we cut world emissions by some factor? The impact and costs of doing nothing or something will not be covered here, but it is obvious they would depend on how fast warming will occur. This we will discuss.
So what are the skeptics skeptical about? It is the amount and rate of the man made warming estimated by the United Nations Intergovernmental Panel on Climate Change (IPCC) and the claims of some spokespeople, many in government, who go much beyond what the IPCC says, like “the planet is having a fever” or “things are getting worse than expected”. But data shows global temperatures have increased much less than models predicted. In fact, unknown to many, accurate satellite data shows very little if any warming in the last 18 years.
Where there is general agreement
There are many areas where most skeptics and the “alarmists”, as they are called, agree. First is the idea of “climate sensitivity”, a useful benchmark for making estimates. It is the final average global temperature rise that would be caused by a doubling of the carbon dioxide (CO2) in the atmosphere, assuming there are no natural changes. Second, most agree on well established methods to estimate how greenhouse gases absorb and emit heat, and that doubling of CO2 will reduce the heat leaving the planet by a little more than 3.5 watts per square meter. This compares to both estimates and satellite measurements of the total now leaving of about 235 watts per square meter. If the value of 3.5 watts out of 235 seems low, it is because CO2 only absorbs the infrared wavelengths that involve about 20% of the heat leaving the surface, and in this region its action is partially saturated and the second doubling will reduce heat loss by about another 3.5, not 7 watts. A 1% change in energy from the sun or a 7% change in cloud cover would cause about the same change as doubling CO2. Third, there is general agreement on how much the average surface will warm to make up for this heat loss: about 1 C (1.8 F). But here is the rub: this estimate is before the atmosphere and the surface, including oceans, react to this temperature change.
Where there is not agreement
How the climate reacts to the initial warming is the main area where most skeptics have problems with the IPCC and others. These reactions are called “feedbacks”. Positive ones amplify any temperature change (warming or cooling from any cause, not just from CO2). Negative ones diminish a change. There are general agreements on the equations used to define the feedback strengths and how they are combined into one net temperature change multiplier that can be either greater or less than one. The major disagreements are the magnitudes of the feedback values and for clouds, even if it is positive or negative. The final IPCC warming estimates for doubling CO2 range from 1.5 to 4.5 C. The skeptics have no common voice, but their values range from about 0.5 to 1.2 C, a significant reduction. IPCC also uses a 1% annual growth of the CO2 content in the atmosphere, while data shows only about 0.55%. This increases CO2 doubling time from about 70 years to 140.
Two different approaches
One primary complaint is the IPCC and most government funding research have abandoned improving the simple energy balance model and the feedback concept and gone to complex climate models that try to estimate many conditions across the globe and layers in the atmosphere over many years and then a temperature change. Small errors can propagate into unknown large ones. There are over 100 of these models written by different teams and their results differ by a range to 3 to 1. And nearly all overestimate warming compared to observed data. This is settled science? No! And it is bad engineering practice, which some scientists apparently don’t understand, to try to solve such a complex problem without breaking it down into smaller steps that each can be verified and corrected. What is causing the errors in the climate models that cause them to overestimate global warming? How will any proposed correction be tested without waiting about 10 to 30 years?
Corrections to the complex computer models
We believe the complex computer models overestimation of warming is mostly based on a combinations of three factors: overestimating positive water vapor feedback, underestimating negative feedback from increased sea surface evaporation and treating cloud feedback as positive feedback while it is very likely negative. For water vapor (a major greenhouse gas) the climate models show it increases about 7% per degree C of warming. But extensive data over 30 years from 15,000 stations at many latitudes over land and sea show an increase of only about 5% at the surface, the atmosphere’s main water vapor source. (Dia, “Recent Climatology and Trends in Global Surface Humidity”, American Meteorological Society, August, 1997). Water vapor is also an absorber of incoming solar energy, reducing what reaches the surface. Reduced greenhouse action and increased solar absorption cut the computer models positive water vapor feedback in about half. Regarding the cooling effects of increased evaporation, mostly over the oceans, both data (Wentz, et al, “How Much More Rain Will Global Warming Bring?, Science, 13 July, 2007) and basic physics indicate an increase of about 6% per degree C of warming, over double what the climate models average. Finally, the models estimate a value of positive feedback for clouds only because this amount is needed to boost the initial 1 C prefeedback warming up to the models final average estimate. It is more likely that more evaporation and water vapor will increase cloud content, a net cooling effect. Using simple energy balance models with proven greenhouse gas absorption/radiation tools, the result of these changes indicates a warming from double CO2 in a range of 0.6 to 0.9 C, much less than IPCC’s value of 1.5 to 4.5 C. Note the uncertainty range drops by a factor of 10, from of 3 degrees C to 0.3 C, because of the elimination of unreliable complex computer models and their net positive feedback.